#!/usr/bin/env node

//可读拉取流
const {Readable} = require('stream');

const rs = new Readable();

let c = 'a'.charCodeAt(0);
rs._read=()=>{
  rs.push(String.fromCharCode(c++));
  if(c==='z'.charCodeAt(0)+1){
    rs.push(null);
  }

}
rs.pipe(process.stdout);
